The guys over at XDA developers have figured out how to get your HTC Evo up and running on verizon.
[6/16]*techknowfile's* - Hack the HTC EVO - 3G w/o Sprint EVDO coverage! - xda-developers
that post will have you download and update a new PRL. i suggest doing a speed test before and after the process, just so you can see which is faster in your area. this is legit. if you dial sprint customer service you will get verizon instead. supposedly this will get you free verizon 3g if you dont have it, or just get you better signal if sprint sucks where you are. ive tried it definitely does work, im seeing 6x speed boosts around my house where sprint has very bad service.
neither i, nor the people at XDA, are responsible for anything bad that happens to you during or after this process. it is probably illegal. sprint could probably drop you, and verizon could most likely sue you, because you are pretty much stealing their network. but from what i can see they cant find out. speed tests show you on the sprint network still. i have my roaming set to sprint only. so im not sure what effect this is going to have on my bill. i think, and people on that thread i linked to seem to agree, that it should be free if all goes well and sprint is none the wiser